A method for evaluating formation rock mechanical properties while drilling based on digital cuttings

Abstract

The embodiment of the present application provides a method, storage medium and processor for evaluating the mechanical properties of formation rocks while drilling based on digital rock cuttings. The method includes: conducting a whole rock analysis experiment to determine the types of minerals included in the rock cuttings; conducting a nanoindentation experiment to obtain the first load displacement curve and elastic modulus of each mineral in the rock cuttings; obtaining the stress-strain curve of each mineral; obtaining a pseudo-color map of the mineral distribution on the surface of the rock cuttings; determining the types of minerals included in each area and the distribution geometric model of each mineral; determining the average strain of each area of ​​the pseudo-color map of the mineral distribution under different confining pressures to obtain the equivalent stress-strain curve of each microscopic area of ​​the rock cuttings; when the mineral proportion of each microscopic area is close to the result of the whole rock analysis experiment, determining the average value of the stress-strain curve of each microscopic area, so as to determine the actual stress-strain curve of the rock cuttings according to the average value of the stress-strain curve of all microscopic areas.

Description

Technical Field

[0001] The present application relates to the technical field of rock mechanics, and in particular to a method, storage medium and processor for evaluating formation rock mechanical properties while drilling based on digital rock cuttings. Background Art

[0002] Accurately evaluating the mechanical properties of formation rock is the fundamental guide for drilling engineering design, and is also the basis for engineering design such as wellbore stability analysis and reservoir reconstruction. Conventional rock mechanics evaluation methods are mainly based on formation coring and are obtained through indoor rock mechanics experiments. This method has high requirements for formation rock samples, and the evaluation has a lag. For non-target layers, there is usually a lack of logging data and formation cores, which leads to the failure of traditional formation rock mechanics evaluation methods and unclear understanding of rock deformation and failure laws. Summary of the invention

[0003] The first aspect of the embodiment of the present application provides a method for evaluating formation rock mechanical properties based on digital cuttings while drilling, the method comprising:

[0004] Carry out whole-rock analysis experiments on the rock cuttings to be analyzed to determine the types of minerals included in the rock cuttings to be analyzed, the components and proportions of each mineral;

[0005] Conduct nanoindentation experiments on the rock cuttings to be analyzed to obtain the first load displacement curve and elastic modulus of each mineral in the rock cuttings to be analyzed;

[0006] The first load displacement curve of each mineral is inverted based on finite element software to obtain the stress-strain curve of each mineral;

[0007] Scan the surface of the rock cuttings to be analyzed to obtain a pseudo-color image of the mineral distribution on the surface of the rock cuttings to be analyzed;

[0008] Divide the mineral distribution pseudo-color map into multiple regions, determine the mineral types included in each region and the distribution geometric model of each mineral;

[0009] Determine the average strain of each area of ​​the mineral distribution pseudo-color map under different confining pressures to obtain the equivalent stress-strain curve of each microscopic area of ​​the rock cuttings to be analyzed;

[0010] Based on the equivalent stress-strain curve, determine whether the mineral proportions in each microscopic area are close to the results of the whole-rock analysis experiment;

[0011] When the mineral proportions of each microscopic region are close to the experimental results of whole-rock analysis, the average value of the stress-strain curve of each microscopic region is determined based on the equivalent stress-strain curve of each microscopic region, so as to determine the actual stress-strain curve of the rock cuttings to be analyzed according to the average value of the stress-strain curves of all microscopic regions.

[0012] In an embodiment of the present application, the method also includes: when the deviation between the equivalent stress-strain curve and the stress-strain curve is less than or equal to a preset distance, determining that the equivalent stress-strain curve is approaching the stress-strain curve; when the deviation between the equivalent stress-strain curve and the stress-strain curve is greater than the preset distance, determining that the equivalent stress-strain curve deviates from the stress-strain curve; when the equivalent stress-strain curve deviates from the stress-strain curve obtained after inversion, combining multiple regions divided by the mineral distribution pseudo-color map to obtain multiple new regions, and re-determining the mineral types included in each region and the distribution geometric model of each mineral; when the equivalent stress-strain curve is approaching the stress-strain curve, determining that the mineral proportion of each microscopic region is approaching the whole rock analysis experiment result.

[0013] In the embodiment of the present application, the elastic modulus E of each mineral in the rock cuttings to be analyzed is calculated according to formula (1):

[0014]

[0015] Where v is the Poisson's ratio of the mineral, E i and v i They are respectively expressed as the elastic modulus and Poisson’s ratio of the indenter, E r Expressed as equivalent elastic modulus.

[0016] In the embodiment of the present application, the equivalent elastic modulus E is calculated according to formula (2): r :

[0017]

[0018] Among them, S represents the elastic contact stiffness, β represents the indenter correction coefficient, and A represents the contact area between the indenter and the cuttings to be analyzed at the peak load moment.

[0019] In an embodiment of the present application, the first load-displacement curve of each mineral is inverted based on finite element software to obtain the stress-strain curve of each mineral, including: constructing a corresponding nanoindentation experimental model based on the geometric and material mechanics parameters of the indenter in the nanoindentation instrument through finite element software; for each mineral, setting multiple groups of stress-strain curves to be tested respectively; for each mineral, inputting each group of stress-strain curves to be tested into the nanoindentation experimental model for numerical simulation to obtain a second load-displacement curve corresponding to each group of stress-strain curves to be tested; for each mineral, determining the second load-displacement curve that matches the first load-displacement curve as the target load-displacement curve; for each mineral, determining the stress-strain curve to be tested corresponding to the target load-displacement curve as the stress-strain curve of the mineral.

[0020] In an embodiment of the present application, determining the average strain of each area of ​​the mineral distribution pseudo-color map under different confining pressures includes: assigning stress-strain curve parameters of each mineral to each mineral based on the stress-strain curve of each mineral, so as to establish a mechanical model that reflects the actual distribution and mechanical properties of various minerals in each microscopic region of the rock cuttings to be analyzed; based on the mechanical model of each microscopic region, setting different confining pressures for each area of ​​the mineral distribution pseudo-color map of each mineral, so as to determine the average strain of each area of ​​the mineral distribution pseudo-color map under different confining pressures.

[0021] In the embodiment of the present application, the method further comprises: after determining the actual stress-strain curve of the rock cuttings to be analyzed, calculating the total proportion of minerals in each microscopic region according to formula (3):

[0022]

[0023] Among them, ω i ′ Expressed as the total mineral proportion, A i is represented by the image area of ​​each microscopic region in the mineral distribution pseudo-color map, ω i It is expressed as the proportion of the i-th type of minerals in each microscopic area, and n is expressed as the number of areas in the mineral distribution pseudo-color map.

[0024] In the embodiment of the present application, the average value of the stress-strain curve of each microscopic region is calculated according to formula (4):

[0025]

[0026] Among them, σ i ′ It is expressed as the stress average value of the stress-strain curve of the i-th microscopic region, σ i It is expressed as the stress corresponding to the i-th microscopic region under the same strain.

[0027] In a second aspect, the present application provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute any of the above-mentioned methods for evaluating formation rock mechanical properties while drilling based on digital cuttings.

[0028] In a third aspect, the present application provides a processor for running a program, wherein when the program is run, any of the above-mentioned methods for evaluating formation rock mechanical properties while drilling based on digital cuttings is executed.

[0029] In this scheme, a method based on digital evaluation of rock mechanical parameters of corresponding formations based on drilling cuttings solves the problem of being unable to obtain rock mechanical parameters of formations due to complex formations and missing logging data, provides guidance for later reservoir reconstruction and fracturing, and provides strong support for safe and efficient drilling processes. In addition, this scheme is simple and easy to implement, and the analysis is highly timely.

[0030] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0032] Figure 1 A schematic diagram of an application environment of a method for evaluating formation rock mechanical properties while drilling based on digital rock cuttings according to an embodiment of the present application is schematically shown;

[0033] Figure 2 A schematic diagram of a process flow of a method for evaluating formation rock mechanical properties while drilling based on digital rock cuttings according to another embodiment of the present application is shown;

[0034] Figure 3A A schematic diagram of load-displacement relationship curves of different minerals measured by a nanoindentation instrument according to an embodiment of the present application is schematically shown;

[0035] Figure 3B A schematic diagram of a nanoindentation experimental model constructed by finite element software according to an embodiment of the present application is schematically shown;

[0036] Figure 4 A schematic diagram showing a comparison of load-displacement relationship curves obtained by finite element software simulation and nanoindentation experiment according to an embodiment of the present application;

[0037] Figure 5 A schematic diagram of stress-strain curves of various minerals obtained by finite element inversion according to an embodiment of the present application is schematically shown;

[0038] Fig. 6A Schematically showing a mineral false color distribution map obtained by scanning the surface of a rock chip slice by AMICS according to an embodiment of the present application;

[0039] Figure 6B Schematically shows a pseudo-color image of mineral distribution of a partially cut-away area according to an embodiment of the present application;

[0040] Figure 6CA pseudo-color image of mineral particle contours after regional fitting according to an embodiment of the present application is schematically shown;

[0041] Figure 7 A mechanical model that reflects the actual distribution and mechanical properties of various minerals in rock cuttings in a partial area according to an embodiment of the present application is schematically shown;

[0042] Figure 8 A schematic diagram schematically shows a stress-strain curve of the entire rock cuttings in a region obtained through numerical simulation according to an embodiment of the present application;

[0043] Fig. 9 The stress-strain curve of the complete rock cuttings of the combined area calculated after combining different numbers of areas according to an embodiment of the present application is schematically shown. DETAILED DESCRIPTION

[0044] The specific implementation of the embodiment of the present application is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present application, and is not used to limit the embodiment of the present application.

[0045] like Figure 1 As shown, a method for evaluating the mechanical properties of formation rock based on digital rock cuttings while drilling is provided. In this embodiment, the method for evaluating the mechanical properties of formation rock based on digital rock cuttings while drilling includes the following steps:

[0046] Step 101, conduct a whole-rock analysis experiment on the rock cuttings to be analyzed to determine the types of minerals included in the rock cuttings to be analyzed, and the components and proportions of each mineral.

[0047] Step 102 : Performing a nanoindentation experiment on the rock cuttings to be analyzed to obtain a first load-displacement curve and an elastic modulus of each mineral in the rock cuttings to be analyzed.

[0048] Step 103: Invert the first load-displacement curve of each mineral based on finite element software to obtain the stress-strain curve of each mineral.

[0049] Step 104 , scanning the surface of the rock cuttings to be analyzed to obtain a pseudo-color image of mineral distribution on the surface of the rock cuttings to be analyzed.

[0050] Step 105, dividing the mineral distribution pseudo-color map into multiple regions, determining the mineral types included in each region and the distribution geometric model of each mineral.

[0051] Step 106 , determining the average strain of each region of the mineral distribution pseudo-color map under different confining pressures, so as to obtain the equivalent stress-strain curve of each microscopic region of the rock cuttings to be analyzed.

[0052] Step 107, judging whether the mineral proportions in each microscopic region are close to the whole rock analysis experimental results based on the equivalent stress-strain curve.

[0053] Step 108, when the mineral proportions of each microscopic region are close to the whole rock analysis experimental results, the average value of the stress-strain curve of each microscopic region is determined based on the equivalent stress-strain curve of each microscopic region, so as to determine the actual stress-strain curve of the rock cuttings to be analyzed according to the average value of the stress-strain curves of all microscopic regions.

[0054] Rock cuttings are formation rocks that are broken by the drill bit and carried out by the drilling fluid during the drilling process. They have the same mechanical properties as the formation rocks. Rock mechanical parameter evaluation of drilling cuttings is more efficient than traditional indoor rock mechanics experiments and can support wellbore instability analysis while drilling. In this embodiment, first, on-site drilling cuttings can be used, and then a whole-rock analysis experiment can be carried out on the cuttings to determine the types of minerals included in the cuttings to be analyzed, the components and proportions of each mineral. Next, a nanoindentation experiment can be carried out on the cuttings to be analyzed to obtain the first load displacement curve and elastic modulus of each mineral in the cuttings to be analyzed. The composition of the cuttings is complex, and there are all kinds of rocks. Mineral fragments are mainly quartz, calcite, dolomite, feldspar, clay minerals, mica and a small amount of heavy minerals, etc. The types of minerals are not limited here, and the specific situation depends on the actual situation.

[0055] In one embodiment, the elastic modulus E of each mineral in the rock fragments to be analyzed can be calculated according to formula (1):

[0056]

[0057] Where v is the Poisson's ratio of the mineral, E i and v i They are respectively expressed as the elastic modulus and Poisson's ratio of the indenter, E r Expressed as the equivalent elastic modulus. In fluid mechanics, head refers to the energy per unit weight of a fluid, which can be the energy due to the height at which the fluid is located, the pressure of the fluid, or the velocity of the fluid.

[0058] In one embodiment, the equivalent elastic modulus E can be calculated according to formula (2): r :

[0059]

[0060] Among them, S represents the elastic contact stiffness, β represents the indenter correction coefficient, and A represents the contact area between the indenter and the cuttings to be analyzed at the peak load moment.

[0061] In one embodiment, Figure 2As shown, a method for evaluating the mechanical properties of formation rocks while drilling based on digital rock cuttings in another embodiment is shown. It can be seen that the step of conducting a nanoindentation experiment on the rock cuttings to be analyzed to obtain the first load displacement curve and elastic modulus of each mineral in the rock cuttings to be analyzed can be performed simultaneously with the step of scanning the surface of the rock cuttings to be analyzed to obtain a pseudo-color map of the mineral distribution on the surface of the rock cuttings to be analyzed, so as to save analysis time and improve analysis efficiency. Specifically, the advanced mineral identification and analysis system (AMICS) can be used to scan the surface of the rock cuttings to be analyzed.

[0062] In one embodiment, Figure 3A As shown, a schematic diagram of the load-displacement relationship curves of different minerals measured by a nanoindentation instrument is provided. It can be seen that the load-displacement relationship curves of different types of minerals obtained under the nanoindentation instrument are different.

[0063] Further, the first load displacement curve of each mineral can be inverted based on finite element software to obtain the stress-strain curve of each mineral. Specifically, in one embodiment, the first load displacement curve of each mineral is inverted based on finite element software to obtain the stress-strain curve of each mineral, including: constructing a corresponding nanoindentation experimental model based on the geometry and material mechanics parameters of the indenter in the nanoindentation instrument through finite element software; for each mineral, setting multiple groups of stress-strain curves to be tested respectively; for each mineral, inputting each group of stress-strain curves to be tested into the nanoindentation experimental model for numerical simulation respectively, to obtain a second load-displacement curve corresponding to each group of stress-strain curves to be tested; for each mineral, determining the second load-displacement curve that matches the first load-displacement curve as the target load-displacement curve; for each mineral, determining the stress-strain curve to be tested corresponding to the target load-displacement curve as the stress-strain curve of the mineral.

[0064] In this embodiment, firstly, a nanoindentation experimental model is constructed using finite element software according to the geometry and material mechanics parameters of the indenter in the nanoindentation instrument. Then, multiple groups of stress-strain curves are set for different types of minerals. Finally, each group of stress-strain curves is input into the constructed model for numerical simulation to obtain the load-displacement curve corresponding to each group until it matches the load-displacement curve obtained by the experiment. At this time, the input stress-strain curve is the stress-strain curve of each mineral obtained by inversion.

[0065] like Figure 3B , which shows a schematic diagram of a nanoindentation experimental model constructed by finite element software in an embodiment. Figure 4As shown, a schematic diagram of the comparison of the load-displacement relationship curve obtained by finite element software simulation and nanoindentation experiment in one embodiment is shown. Among them, the solid line represents the load-displacement relationship curve measured by the nanoindentation instrument. The dotted line represents the load-displacement relationship curve obtained by finite element software simulation. Figure 5 , which is a schematic diagram of stress-strain curves of various minerals obtained by finite element inversion in one embodiment.

[0066] After obtaining the rock cuttings to be analyzed, the surface of the rock cuttings to be analyzed can be scanned to obtain a pseudo-color map of the mineral distribution on the surface of the rock cuttings to be analyzed. Specifically, the Advanced Mineral Identification and Analysis System (AMICS) can be used to scan the surface of the rock cuttings to be analyzed. The AMICS test principle is: the energy spectrum curve is measured at a certain point on the sample surface, and compared with the typical energy spectrum curves of various minerals in the mineral standard library to obtain the possible mineral type at the point; the sample is analyzed point by point to form a pseudo-color map of the mineral distribution, that is, different colors are used to represent different minerals. Fig. 6A FIG. 1 shows a mineral pseudo-color distribution map obtained by scanning the surface of a rock chip slice by AMICS in one embodiment.

[0067] After obtaining the mineral distribution pseudo-color map of the surface of the rock fragments to be analyzed, the mineral distribution pseudo-color map can be divided into multiple regions, so that the mineral types included in each region and the distribution geometric model of each mineral can be determined. Specifically, the mineral distribution pseudo-color map can be cut into multiple regions, and the distribution geometric model of each mineral in each region can be obtained by using methods such as image processing and polygon fitting. Among them, the image processing method includes image denoising, image segmentation and edge detection; the polygon fitting method includes least squares method and contour approximation method. Figure 6B A pseudo-color image of mineral distribution of a partially cut-away area in one embodiment is shown. Figure 6C A pseudo-color image of mineral particle contours after region fitting in one embodiment is shown.

[0068] After determining the mineral types included in each area and the distribution geometric model of each mineral, the average strain of each area of ​​the mineral distribution pseudo-color map under different confining pressures can be determined to obtain the equivalent stress-strain curves of each microscopic area of ​​the rock cuttings to be analyzed.

[0069] In one embodiment, determining the average strain of each region of the mineral distribution pseudo-color map under different confining pressures includes: assigning stress-strain curve parameters of each mineral to each mineral based on the stress-strain curve of each mineral to establish a mechanical model that reflects the actual distribution and mechanical properties of various minerals in each microscopic region of the rock cuttings to be analyzed; and setting different confining pressures for each region of the mineral distribution pseudo-color map of each mineral based on the mechanical model of each microscopic region to determine the average strain of each region of the mineral distribution pseudo-color map under different confining pressures.

[0070] Among them, the stress-strain curve parameters of each mineral include strain and stress corresponding to the strain, and may also include elastic modulus, yield strain (strain when entering the plastic stage), etc. The number and type of parameters are not limited here and can be changed accordingly according to actual project needs. Specifically, the mineral distribution geometry model includes multiple closed polygonal areas. For different types of minerals, the above-mentioned stress-strain curve parameters can be assigned to the corresponding closed area in the closed area, and the boundary conditions on the mineral boundary can be set, so that a mechanical model that reflects the actual distribution and mechanical properties of various minerals in each microscopic area of ​​the cuttings to be analyzed can be established. This mechanical model can also be called digital cuttings. Figure 7 As shown, a mechanical model of a partial area in an embodiment reflects the actual distribution and mechanical properties of various minerals in rock cuttings. Figure 8 , which is a schematic diagram of a stress-strain curve of the entire rock cuttings in a region obtained by numerical simulation in one embodiment.

[0071] For the rock cuttings to be analyzed, by placing them under a microscope or other equipment, their surface can be divided into multiple regions, which can also be called multiple microscopic regions due to their small area. Furthermore, based on the mechanical model of each microscopic region on the rock cuttings surface, different confining pressures are set for each region of the mineral distribution pseudo-color map of each mineral to determine the average strain of each region of the mineral distribution pseudo-color map under different confining pressures. Fig. 9 , which shows the stress-strain curve of the complete rock cuttings of the combined area calculated after combining different numbers of areas in one embodiment.

[0072] After obtaining the equivalent stress-strain curves of each microscopic region of the rock cuttings to be analyzed, it is possible to determine whether the mineral proportion of each microscopic region is close to the whole rock analysis experimental results based on the equivalent stress-strain curves. Since the equivalent stress-strain curves obtained by combining different regions after the mineral distribution pseudo-color map is divided into multiple regions will be different, it is possible to determine whether the mineral proportion of each microscopic region under the combination is close to the whole rock analysis experimental results based on the equivalent stress-strain curves. In the case where the mineral proportion of each microscopic region is close to the whole rock analysis experimental results, the average value of the stress-strain curve of each microscopic region can be determined based on the equivalent stress-strain curve of each microscopic region, so as to determine the actual stress-strain curve of the rock cuttings to be analyzed based on the average value of the stress-strain curves of all microscopic regions.

[0073] In one embodiment, when the deviation between the equivalent stress-strain curve and the stress-strain curve is less than or equal to the preset distance, it can be determined that the equivalent stress-strain curve is close to the stress-strain curve; when the deviation between the equivalent stress-strain curve and the stress-strain curve is greater than the preset distance, it is determined that the equivalent stress-strain curve deviates from the stress-strain curve. In the case where the equivalent stress-strain curve deviates from the stress-strain curve obtained after inversion, multiple regions divided by the mineral distribution pseudo-color map are combined to obtain multiple new regions, and the mineral types included in each region and the distribution geometric model of each mineral are determined again. Among them, the value of the preset distance can be set based on the actual project. In other words, if it is determined that the equivalent stress-strain curve does not approach the stress-strain curve, multiple small regions can continue to be combined until the equivalent stress-strain curve approaches the stress-strain curve. The upper limit of the number of combined small regions can be determined based on the actual project, and is not limited here. In the case where the equivalent stress-strain curve approaches the stress-strain curve, it can be determined that the mineral proportion of each microscopic region is close to the whole rock analysis experiment result.

[0074] In one embodiment, the method further comprises:

[0075] After determining the actual stress-strain curve of the rock cuttings to be analyzed, the total proportion of minerals in each microscopic area is calculated according to formula (3):

[0076]

[0077] Among them, ω i ′ Expressed as the total mineral proportion, A i is represented by the image area of ​​each microscopic region in the mineral distribution pseudo-color map, ω i It is expressed as the proportion of the i-th type of minerals in each microscopic area, and n is expressed as the number of areas in the mineral distribution pseudo-color map.

[0078] In one embodiment, the average value of the stress-strain curve of each microscopic region is calculated according to formula (4):

[0079]

[0080] Among them, σ i ′ It is expressed as the stress average value of the stress-strain curve of the i-th microscopic region, σ i It is expressed as the stress corresponding to the i-th microscopic region under the same strain.

[0081] In this scheme, the method of evaluating the rock mechanical parameters of the corresponding formation based on the digitalization of drilling cuttings solves the problem of being unable to obtain the rock mechanical parameters of the formation due to the complexity of the formation and the lack of logging data, provides a guiding basis for the later reservoir transformation and fracturing, and provides strong support for the safe and efficient drilling process. In addition, this scheme is simple and easy to implement, and the analysis is highly timely. In addition, this scheme uses a series of digital methods to digitize the microstructure of the cuttings, greatly reducing the cost of storing and calling cuttings data. The digital cuttings model provides a large amount of original data and a true and accurate basis for subsequent research on the cuttings.

[0082] In one embodiment, a device for evaluating formation rock mechanical properties while drilling based on digital rock cuttings is provided, the device comprising:

[0083] a memory configured to store instructions; and

[0084] The processor is configured to call the instructions from the memory and implement any one of the above-mentioned methods for evaluating formation rock mechanical properties while drilling based on digital rock cuttings when executing the instructions.

[0085] The processor includes a kernel, which retrieves the corresponding program unit from the memory. One or more kernels can be set, and the mechanical properties of the formation rock can be evaluated based on digital cuttings while drilling by adjusting kernel parameters.

[0086] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0087] An embodiment of the present application provides a storage medium on which a program is stored. When the program is executed by a processor, the method for evaluating the mechanical properties of formation rocks while drilling based on digital cuttings is implemented.

[0088] An embodiment of the present application provides a processor, which is used to run a program, wherein the program, when running, executes the method for evaluating formation rock mechanical properties while drilling based on digital cuttings.

[0089] An embodiment of the present application provides a device, which includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, the following steps of a method for evaluating formation rock mechanical properties while drilling based on digital cuttings are implemented.

[0090] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program that initializes the method steps for evaluating formation rock mechanical properties while drilling based on digital rock cuttings.

[0091] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0092] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0093] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0094] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0095] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0096] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0097] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0098] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0099] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for evaluating formation rock mechanical properties based on digital cuttings while drilling, characterized in that: The method comprises: Conducting a whole-rock analysis experiment on the rock cuttings to be analyzed to determine the types of minerals included in the rock cuttings to be analyzed, as well as the components and proportions of each mineral; Conducting a nanoindentation experiment on the rock cuttings to be analyzed to obtain a first load-displacement curve and an elastic modulus of each mineral in the rock cuttings to be analyzed; The first load displacement curve of each mineral is inverted based on finite element software to obtain the stress-strain curve of each mineral; Scanning the surface of the rock cuttings to be analyzed to obtain a pseudo-color image of mineral distribution on the surface of the rock cuttings to be analyzed; Dividing the mineral distribution pseudo-color map into a plurality of regions, determining the mineral types included in each region and the distribution geometric model of each mineral; Determine the average strain of each region of the mineral distribution pseudo-color map under different confining pressures to obtain an equivalent stress-strain curve of each microscopic region of the rock cuttings to be analyzed; Based on the equivalent stress-strain curve, it is judged whether the mineral proportion of each microscopic area is close to the whole rock analysis experiment result; When the mineral proportions of each microscopic region are close to the experimental results of whole-rock analysis, the average value of the stress-strain curve of each microscopic region is determined based on the equivalent stress-strain curve of each microscopic region, so as to determine the actual stress-strain curve of the rock cuttings to be analyzed according to the average value of the stress-strain curves of all microscopic regions.

2. The method according to claim 1, characterized in that The method further comprises: When a deviation between the equivalent stress-strain curve and the stress-strain curve is less than or equal to a preset distance, determining that the equivalent stress-strain curve is approaching the stress-strain curve; When the deviation between the equivalent stress-strain curve and the stress-strain curve is greater than the preset distance, determining that the equivalent stress-strain curve deviates from the stress-strain curve; In the case where the equivalent stress-strain curve deviates from the stress-strain curve obtained after the inversion, the multiple regions divided by the mineral distribution pseudo-color map are combined to obtain multiple new regions, and the mineral types included in each region and the distribution geometric model of each mineral are determined again; When the equivalent stress-strain curve approaches the stress-strain curve, it is determined that the mineral proportions of each microscopic region are close to the whole rock analysis experimental results.

3. The method according to claim 1, characterized in that The elastic modulus E of each mineral in the rock cuttings to be analyzed is calculated according to formula (1): Where v is the Poisson's ratio of the mineral, E i and v i They are respectively expressed as the elastic modulus and Poisson’s ratio of the indenter, E r Expressed as equivalent elastic modulus.

4. The method according to claim 3, characterized in that The equivalent elastic modulus E is calculated according to formula (2): r : Wherein, S represents the elastic contact stiffness, β represents the indenter correction coefficient, and A represents the contact area between the indenter and the rock cuttings to be analyzed at the peak load moment.

5. The method according to claim 1, characterized in that The inversion of the first load displacement curve of each mineral based on finite element software to obtain the stress-strain curve of each mineral includes: The corresponding nanoindentation experimental model is constructed based on the geometry and material mechanics parameters of the indenter in the nanoindentation instrument using finite element software; For each mineral, multiple groups of stress-strain curves to be tested are set up respectively; For each mineral, each set of stress-strain curves to be tested is input into the nanoindentation experimental model for numerical simulation to obtain a second load-displacement curve corresponding to each set of stress-strain curves to be tested; For each mineral, determining a second load-displacement curve that matches the first load-displacement curve as a target load-displacement curve; For each mineral, the stress-strain curve to be tested corresponding to the target load-displacement curve is determined as the stress-strain curve of the mineral.

6. The method according to claim 1, characterized in that Determining the average strain of each region of the mineral distribution pseudo-color map under different confining pressures comprises: Based on the stress-strain curve of each mineral, the stress-strain curve parameters of each mineral are assigned to each mineral to establish a mechanical model reflecting the real distribution and mechanical properties of each type of mineral in each microscopic region of the rock cuttings to be analyzed; Based on the mechanical model of each microscopic region, different confining pressures are set for each region of the mineral distribution pseudo-color map of each mineral to determine the average strain of each region of the mineral distribution pseudo-color map under different confining pressures.

7. The method according to claim 1, characterized in that The method further comprises: After determining the actual stress-strain curve of the rock fragments to be analyzed, the total proportion of minerals in each microscopic area is calculated according to formula (3): Among them, ω i ′ Expressed as the total mineral proportion, A i Expressed as the image area of ​​each microscopic region in the mineral distribution pseudo-color map, ω i It is represented as the proportion of the i-th type of mineral in each microscopic area, and n is represented as the number of areas in the pseudo-color map of the mineral distribution.

8. The method according to claim 1, characterized in that The average value of the stress-strain curve of each microscopic area is calculated according to formula (4): Among them, σ i ′ It is expressed as the stress average value of the stress-strain curve of the i-th microscopic region, σ i It is expressed as the stress corresponding to the i-th microscopic region under the same strain.

9. A machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the method for evaluating formation rock mechanical properties while drilling based on digital cuttings as described in any one of claims 1 to 8 of the present application.

10. A processor, characterized in that: Used to run a program, wherein the program, when run, is used to execute the method for evaluating formation rock mechanical properties while drilling based on digital cuttings as described in any one of claims 1 to 8.

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